Since some version of Linux (I think since some 5.x), my computer 
started to turn off randomly, especially when under a load. A workaround 
is to put it into power saving mode (using Power in Gnome Settings). 
This makes it almost 2 times slower.

Unmodified Asus X515EA. I recently updated BIOS to Asus's version 315, 
but this didn't help.

Previously we cleared it from dust and replaced the thermal paste, but 
that didn't fix the problem.

I am attaching dmidecode.